In a spark plug, a voltage is applied between a center electrode and a ground electrode that are insulated from each other by an insulator, and thereby a spark occurs at a gap formed between the front end part of the center electrode and the front end part of the ground electrode. As the ground electrode of the spark plug, there has been known a configuration in which a projection part projecting toward the center electrode from a ground electrode body is provided and the end part of the projection part forms the gap. Providing the projection part results in a longer distance between the gap and the ground electrode body. As a result, it is suppressed that the growth of a flame generated at the gap is restricted by the ground electrode body, so that ignitability of the spark plug can be improved. Further, the end part of the projection part is formed by using a noble metal, so that the wear resistance can be improved.